Sex-for-grades trial: Darinne Ko takes the witness stand

The female student at the centre of the sex-for-grades saga has been called to the witness stand.

She is one of 14 witnesses who will be testifying at the trial against law professor Tey Tsun Hang, which started on Thursday morning.

Ms Darinne Ko Wen Hui is expected to give her version of events, which eventually led to Tey being faced with six charges of corruptly obtaining sex and gifts from her in exchange for better grades.

The 23-year-old managed to slip by the media pool waiting for her arrived outside of the Subordinate Courts in the morning.

Tey, 41, returned to the courtroom after a short break in proceedings earlier, dressed in a long black lawyer's robe.

He had arrived in court earlier wearing a light grey suit.

The former associate professor at the National University of Singapore, also set up a small easel for documents in front of him as he prepares to defend himself in court.

The dramatic twist came barely an hour into first day of the nine-day hearing, after Tey's lawyer Peter Low told the court on his client's behalf, that Tey would like to "play an active role" in court proceedings.

When asked to elaborate, Mr Low explained that Tey would like to cross-examine some of the prosecution witnesses, to which the prosecution objected since he is already represented by defence counsel.

Tey then told the court that he would discharge Mr Low as his lawyer and told the court that he will fight the case on his own.

He has since decided to retain Mr Low, but will conduct his own defence in the case.

The offences Tey allegedly committed took place between May and July 2010.